Electric fuse



April 22, 1947. E P, BRUS f 2,419,251

ELECTRIC FUSE Filed Nov. l, 1943 INVENTOR. 5727/@ @f4/.5

ATTO NEY.

Patented Apr. 22, 1947 UNITED STATES PATENT OFFICE ELECTRIC FUSE Emile P. Brus, Kansas City, Mo.

Application November 1, 1943, Serial No. 508,537

(Cl. ZOO- 130) 9 Claims.

This invention relates to electric fuses of the type wherein the fusible element may be replaced by the user in the event of a circuit overload, without disposing of any of the housing parts constituting the fuse assembly.

This application is a continuation in part of my co-pending application Serial No. 457,283, filed September Ll, 1942, for Renewable fuse plug.

One of the important aims of the instant invention is the provision of an electric fuse having as a part thereof, means for supporting the fusible element that is safe, efficient and incapable of rendering the fuse assembly inoperative after long and continued use.

The portion of the renewable fuse plug shown and described by my above identified application and upon which is mounted the fusible element,

is molded of material capable of easy manipula-- tion, which necessitates the employment of substance having a relatively low melting point andr which carbonizes upon the application of heat due to fusing of the element.

The fuse embodying the improvements contemplated by this invention, will not foul due to the application of heat, and therefore, it is one of the salient objects to provide a fusible element holder that may be molded in conventional fashion yet have as a part thereof, a non-carbonizable support.

Further objects of the invention and specific details of construction forming important parts of the electric fuse, will be made clear during the course of the following specification, referring to the accompanying drawing, wherein:

Fig. 1 is an end elevational View of an electric fuse made in accordance with this invention.

Fig. 2 is a longitudinal central sectional View of the same taken on line lil-II of Fig. 1.

Fig. 3 is a stretch-out in perspective of the component parts of the electrical fuse.

Fig. 4 is a cross sectional view taken on line IV-IV of Fig. 2.

Fig, 5 is a similar sectional View taken on line V-V of Fig. 2; and

Fig. 6 is a plan view of the fusible element illustrating the same in a stretched-out condition.

In the preferred embodiment of the invention, the fuse comprises a hollow body, broadly designated by the numeral Iii, within the hollow I2 whereof is disposed a plug I4 of insulating material. This plug is thinible-shaped and has a perforation I6 formed axially through the end wall thereof. This said end wall has an annular outwardly directed flange I3 upon the outer face whereof is provided serrations 2D.

' present.

Flange IB has a slot 22 created therethrough in continuation of a groove 24 provided longitudinally along the side wall of plug I4. This side wall has a longitudinal slot 26 diametrically opposed to groove 24, which is closed for a portion of its length by a tubular insert 2B, which is in telescoping relation with plug I4, as illustrated in Fig. 2.

The inner end of insert 23 rests upon a shoulder .it within plug I4 and the outer end of insert 28 extends a distance beyond the free edge of the side wall of the thimble-shaped plug I4. When plug I4 is fitted into the hollow housing I0, flange i8 rests upon the annular lip of housing I0. The cylindrical, cup-shaped member 32 of conducting material is in screw-threaded relation with the outer face of body lil and serves to hold plug I4 in place. The cylinder 32 has an inwardly disposed overhanging continuous serrated flange 34 which engages serrations 251 when the parts are assembled. f

After body It and cylinder 32 have been secured together with plug I4 in place, the screw-threaded contact post 33 is moved to position through the perforation 33 of plate 43. This plate 40 is of insulating material and when post 36 is tightened in nut 152, all of the elements of the fuse will be locked together.

Nut 42 is of conventional character and is partially embraced by a portion of the link of fusible element 44 near one end thereof. This fusible element has an opening 46 to receive post 36 and when in the normal operative position, a portion of element 44 lies between nut 42 and the inner face of the end wall of plug I4.

Element 44 has a reduced portion 48 which is held in bridging relation to the insert 28 and when an overload is encountered, the element 44 will fuse or melt along that section. While one end of element d4 is engaged by nut 42, as above set down, the other end extends out through slot 22 into engagement with cylinder 32 to complete the assembly,

Lines of weakness across elerneni-I 44 on each side of reduced portion 48 are established by perforations 5S. These lines of weakness are spaced distances apart equal to the diameter of insert 28 or equal to the distance between the outer supporting faces of this insert 28, which engage element 44 to hold the reduced portion 43 thereof in spaced relation with the plug I4. Thus, element A44 may be bent and threaded with ease and no danger of maladjustment between supporting insert 28 and reduced portion 48 is When so threaded, with reduced portion 48 disposed across the lower edge of insert 28, no part of this portion will contact plug I4 because insert 28 extends e, distance beyond the free edge of plug I4.

Plug I4 is molded from substances such as Bakelite or material easily manipulated in molds of conventional type. All of such substances are sinterable and produce carbon when subjected to intense heat and very often the sintering of element M deposits carbon which serves as a conducting material for current-therefore, even after the element i4 has parted at the reduced portion 43 thereof, current may continue to flow due to the formation of carbon by the burning of the molded plug I rl. Any substance that will not sinter and carbonize wo-uld be difficult to mold and expensive equipment would be necessary, especially where a side mold blade is used in the production of plug Ul. Therefore, the tubular insert 28 is used and may be positioned at the time plug I4 is molded or thereafter.

It has been found in practice that insert 2S may be cut from conventional commercial ber tubing, which of course, has a relatively high sintering point with respect to Bakelite or substances of like character from which plug I4 is created.

The melting of element M will not sinter and carbonize the supporting end of insert a8, and therefore, danger of producing a path of travel for the current after the fuse has blown is eliminated.

It is obvious that the broad idea of' providing a special non-carbonizable substance to support fusible element l might be embodied in structures different from that illustrated in the drawing and above described, and therefore, it is desired to be limited only by scope of the appended claims.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

l. An electric fuse of the type specied comprising a hollow body of insulating material; a removable plug of insulating material within the hollow of the body; a fusible element carried by the plug with a weakened length thereof extending across one end of the plug; a member of conducting material mounted on the body, having connection with one end of the fusible element and serving to hold the removable plug in place; a contact post on the plug in connection with the other end o-f the fusible element; and a part on the plug for holding the said weakened length out of contact with the proximal end of the plug, said part having spaced apart points of contact with the fusible element whereby to freely suspend a major portion of the weakened length of the element, said part being formed of substance having a relativ-ely high combustion point whereby to avoid residue when the fusible element is melted during an electrical overload.

2. An electric fuse of the type specied comprising a hollow body of insulating material; a plug of insulating material projecting into the hollow body and provided with a bore; a fusible element extending across one end of the plug and bridging the bore of the plug; a contact post on the plug in connection with one end of the fusible element; a member of conducting material mounted on the body and having connection with the fusible element at its other end; and an insert of insulating substance within the said bore of the plug for holding the bridging portion of the fusible element spaced from said plug, said insert being formed of substance having a relatively high sintering point with respect to the melting point of the fusible element.

3. An electric fuse of the type specified comprising a hollow body of insulating material; a plug of insulating material projecting into the hollow body and provided with a bore; a fusible element extending across one end of the plug and bridging the bore of the plug; a contact post on the plug in connection with one end of the fusible element; a member of conducting material mounted on the body and having connection with the fusible element at its other end; and an insert of insulating substance within the said bore of the plug for holding the bridging portion of the fusible element spaced from said plug, said insert being formed of substance sinterable at a temperature higher than the melting point of the said fusible element.

e. An electric fuse of the type specified cornprising a hollow body of insulating material; a plug of insulating material projecting into the hollow body and provided with a bore; a fusible element extending across one end of the plug and bridging the bore of the plug; a contact post on the plug in connection with one end of the fusible element; a member of conducting material mounted on the body and having connection with the fusible element at its other end; and an insert of insulating substance within the said bore of the plug for holding the bridging portion of the fusible element spaced from said plug, said plug being molded of substance having a relatively low sintering point, the said insert being formed of substance having a relatively high sintering point n respect to the melting point of the fusible element.

5. An electric fuse of the type specified comprising a hollow body of insulating material; a

x plug of insulating material projecting into the hollow body and provided with a bore; a. fusible element extending across one end of the plug and bridging the bore of the plug; a contact post on the plug in connection with one end of the fusible element; a member of conducting material mounted on the body and having connection with the fusible element at its other end; and an insert of insulating substance having a relatively high sintering point with respect to the melting point with respect to the fusible element Within the said bore of the plug for holding the bridging portion of the fusible element spaced from said plug, said plug having shoulders formed on the inner face thereof engagement with one end of the inse-rt to hold the other end thereof spaced outwardly from the said one end of the plug.

6. An electric fuse oi the type specified comprising a hollow body of insulating material; a. plug of insulating material projecting into the hollow body and provided with a bore; a fusible element extending across one end of the plug and bridging the bore of the plug; a contact post on the plug in connection with one end of the fusible element; a member of conducting material mounted on the body and having connection with the fusible element at its other end; and an insert of insulating substance having a relatively high sintering point with respect to the melting point with respect to the fusible element within the said bore of the plug for holding the bridging portion of the fusible element spaced from said plug, said fusible element having a portion of reduced cross section in the bridging portion thereof.

'7. An electric fuse of the type specified comprising a hollow body of insulating material; a plug of insulating material projecting into the hollow body and provided with a bore; a fusible element extending across one end of the plug and bridging the bore of the plug; a contact post on the plug in connection with one end of the fusible element; a member of conducting material mounted on the body and having connection with the fusible element at its other end; and an insert of insulating Substance within the said bore of the plug for holding the bridging portion of the fusible element spaced from said plug, said fusible element having a portion of reduced cross section in the bridging portion thereof, said fusible element having a weakened portion on each side of the portion of reduced cross section, said insert having spaced supporting surfaces for the fusible element, said weakened portions being spaced apart a distance equal to the distance between said supporting surfaces on the insert.

8. An electric fuse of the type specified comprsing a, hollow body of insulating material; a thimble-shaped plug of insulating material having a perforated end wall, projecting into the hollow body and provided with a longitudinal slot through the side wall thereof; a tubular insert shorter than the depth of the plug, fitted into the plug and having a portion of its length at one end projecting outwardly beyond the edge o-f the plug; a fusible element having a weakened section, partially circumscribing the plug end having one end thereof extending into the plug through the slot thereof between the other end of the insert and the end wall of the thimble-shaped plug; a cylinder of conducting material in telescoping relation with the body and bearing against the other end of the fusible element; and a contact post fitted through the perforation of the plug and into engagement with the end of the fusible element, said weakened section being suspended across the outer end of said tubular insert, said insert being of substance having a, relatively high 6 sintering point with respect to the melting point of the fusible element.

9. An electric fuse of the type specied coniprising a hollow body of insulating material; a thirnble-shaped plug of insulating material having a perforated end wall, projecting into the hollow body, and provided with a longitudinal slot through the side wall thereof; a tubular insert shorter than the depth of the plug, fitted into the plug and having a portion of its length at one end projecting outwardly beyond the edge of the plug; a fusible element having a weakened section partially cireumscribing the plug end having one end thereof extending into the plug through the slot thereof between the other end of the insert and the end wall of the thimble-shaped plug; a cylinder of conducting material in telescoping relation with the body and bearing against the other end of the fusible element; a screw-threaded contact post fitted through the perforation of the plug; and a nut threaded onto the post within the plug, ,a portion of the length of the element at said one end thereof being between the nut and the plug and having a hole therethrough for the reception of the post, said weakened section of the fusible link being suspended across the outer end of said tubular insert.

EMILE P. BRUS.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS f' Number Name Date 1,495,682 Goodwin Feb, 7, 1922 1,860,237 Davis May 24, 1932 2,108,106 Dalcher Feb. 15, 1938 2,170,168 Vanderveer Aug. 22, 1939 1,753,046 Eustice Apr. 1, 1930 2,013,147 Goodwin Sept. 3, 1935 

